Method Of Controlling The Essential Radon Parameters In Small Radon Chamber

In the natural radiation exposure of human body,more than 50%of it is contributed by radon and its progeny.Comparing with the radiation dose contributed by radon progeny,the dose contributed by radon itself could be ignored.For evaluating the radon progeny contamination level,various radon progeny monitors were invented,therefore,the reliability and accuracy of data achieved by radon progeny monitors is critical.Hence,it’s necessary to build a device which is able to control the radon progeny state parameter steadily for the calibration and performance test of radon progeny monitors.In foreign countries,large radon chambers with the volume of30m³were build up to calibrate and test radon and radon progeny monitors.Those large radon chambers have preferable stability and progeny space distribution uniformity.However,the radon source activity used in large radon chamber is 10⁶Bqcommonly,control period lasts long and construction cost is high.In order to overcome those disadvantage of large radon chamber mentioned above,it’s useful and valuable to build upa small radon chamber with the volume of1m³ for the calibration and performance test of radon and its progeny monitors.In this paper,a method of controlling the concentration,equilibrium factor and unattached fraction of radon progeny by means of changing the total ventilation rate and aerosol particle concentration in chamber was established,and the method was based on the movement and change principle of radon progeny in air.Theoretical model of the method was established and simulation calculation of control range of radon progeny state parameter was conducted by Matlab programming.Simulation result showed that the range of aerosol particle concentration in small chamber could be varying from10⁸m^-3to10¹⁰m^-3by changing the total ventilation rate and aerosol inlet concentration in small chamber;radon concentration varied from10²Bq?m^-3to10⁴Bq?m^-3by changing the radon source activity and total ventilation rate;equilibrium factor could vary from.002to.025,equilibrium equivalent concentration of radon could vary from10⁰Bq?m^-3to10³Bq?m^-3,unattached fraction could vary from%5to60%.Simulation demonstrated that it was able to control the state parameter of radon progeny in small chamber,the control range was wide enough to reach the requirement raised by the national standard EJ/T-1010-96,and this method could be used to build small radon chamber conducting radon progeny state parameter control experiment.